I don't know if there is an easy way to fix that, if it not just local to the area you have cut.
Drill holes through the glass and inject epoxy with a syringe into the space and draw up with screws, then remove the screws and repair the holes and deck.
I would also prop it up from below.
I don't even know if this is a permanent solution
Someone smarter than me should chime in

You might be able to inject thickened epoxy from the crack opening with large syringes available from Amazon with an extension tip added to get deeper into the crack. Try to determine how deep the delamination is. Start clamping at the gap shown in your picture with plywood on top an bottom to spread the pressure so that the epoxy gets forced into the crack deeper. You may still need to screw the laminate together. The syringes are made for refilling ink cartridges I believe. They are super handy.

Not so sure you are actually seeing delam there? Is it possible you are just looking at an air gap between the deck and the hull/liner as it may have been built? Is there wood fiber/veneer stuck to the underside of the underside of the deck glass?

^^^^^ I was thinking the same thing. does the fiberglass or plywood look torn up with strings of the other material stuck to the other?

Doesnt look like Delam to me either.

At least its dry!